Trenchant argument is of vital importance at all times, but even more so in this time of crisis.

The last year has been very difficult for Israel internationally. All indicators show that its international standing is worse than ever; research shows that a number of delegitimization campaigns are active against the State of Israel. The question of what to do about this is serious and has been preoccupying Israel's politicians and diplomats as well as many Jews around the world who want to be of help.

In this time of rising anxiety Israel's political echelon has taken a number of steps toward undermining Israel's sometimes flawed but always vibrant democracy. The Knesset's shameful passing of Yisrael Beiteinu's so-called Nakba Law in a first reading is a dangerous precedent: Once freedom of expression starts to be curtailed, a state enters a slippery slope and nobody can know where it ends. The Israel Defense Forces' declaring Bil'in a closed military area is an active step against political freedom and a way to undercut decisions taken by Israel's Supreme Court.

This tendency is reflected in developments in world Jewry. The new pro-Israel, pro-peace lobby J Street has been critical of many of Israel's actions, particularly settlement expansion and construction in East Jerusalem. Many reactions have been dismaying: Instead of engaging with J Street, Israel's ambassador to the United States chose not to attend its first convention because he believes that it endangers Israel's interests. Others again have argued that J Street misrepresents its position by calling itself pro-Israel and is another instance of Jewish self-hatred.

This profoundly worrying delegitimization campaign against Jewish and Israeli liberals is taking many forms: A number of Web sites track anti-Israeli activities and positions among Israeli academics. The sites' tone is remarkably reminiscent of the style of Joseph McCarthy's investigations into "un-American activities" in the 1950s, a stain in the history of the world's leading democracy. In some of the cases the coverage is formulated in inflammatory language, in others it is highly inexact.

A good example is the vicious campaign that has been launched against Tel Aviv University historian Shlomo Sand, who wrote a book arguing that Israel needs to move from an ethnocentric to a liberal model of democracy. Sand has been called anti-Semitic and a "self-hating Jew" - even though it seems from the utter inexactness of some of the claims on these Web sites that few of the delegitimizers have actually read the book. As a result, these attacks completely miss the simple point that Sand's goal is precisely to ensure the existence of Israel as a democratic state with a Jewish majority!

To restate the obvious: In a democracy, every public statement that does not incite violence or actively promote hatred is legitimate. The essence of democracy is that the public domain is open to conflicting opinions. This is why, in a truly democratic regime, there is always an opposition. Only in pseudo-democracies like Syria is the president elected unanimously, and only the government's line is allowed. John Stuart Mill, the classic theorist of liberal democracy, has argued forcefully that no democracy can allow itself to shut up dissent, and his argument is valid to this day.

It is necessary to restate the obvious because many well-meaning Diaspora Jews feel that the only way to be loyal to Israel is to support its policies, no matter what they are. They often take their cues from one-sided, unreliable sources, and have taken the line that all criticism emanating from Jews, whether in Israel or the Diaspora, reflects disloyalty to both Jewry and Israel. Such an approach is both undemocratic and opposed to the Jewish ethos of incisive and trenchant argument.

It is also profoundly counterproductive: No group should claim the prerogative of having a monopoly on what it means to be a good Jew or to act in Israel's interest. Trenchant argument is of vital importance at all times, but even more so in this time of crisis. Trying to shut up those who disagree with you by delegitimizing them is morally wrong, politically dangerous and inexpedient because it doesn't allow for the critical discussion sorely needed.

Behind all this highly charged and often inflammatory rhetoric is a deep sentiment of anxiety. We are all worried about Israel's standing in the world, and we all care about its safety. I emphasize "we all": This includes both the right, with which I disagree but which I don't delegitimize, and the liberal camp, to which I belong, even though I disagree with the lines of action and argument of some of its members.

Both sides believe that they have the correct views about what is good for Israel in the short and long term. But those on the right who, however well-meaning, try to delegitimize the liberal camp may end up unintentionally harming one of Israel's greatest assets: its democracy.

The writer is chair of the Clinical Graduate Program at Tel Aviv University. His recent paper "Knowledge-Nation Israel: A New Unifying Vision" has been published by Azure.

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